I'm not going to sit here and say lead is safe or that exposure is not a big deal. The truth is the levels of lead in food are at a 50-year low — and yet there is still real reason to track your exposure. The trick is knowing which standard you're being told to compare against, and why.
Why there are multiple "limits" for lead
If you've seen different lead numbers cited online and they don't agree, that's because there isn't one number. There are several, each defined for a different purpose.
| Source | Daily threshold | Based on | Use case |
|---|---|---|---|
| FDA IRL (children) | 2.2 µg/day | Blood lead biokinetic modeling | Risk evaluation in food/supplements |
| FDA IRL (women, reproductive age) | 7.7 µg/day | Blood lead biokinetic modeling | Risk evaluation in food/supplements |
| California Prop 65 MADL | 0.5 µg/day | Reproductive toxicity threshold | Consumer warning labels |
| "Lead Safe Mama" benchmark | 5 PPB in baby food | Ultra-precautionary, advocacy | Alarming people without dose context |
| WHO PTWI (deprecated) | ~250 µg/week (10 kg child) | Tolerable weekly intake | Withdrawn 2010 — no safe level |
The FDA Interim Reference Levels
The FDA's Interim Reference Levels (IRLs) are the risk-evaluation numbers I usually use when reasoning about specific food exposures.
- 2.2 µg/day for children
- 7.7 µg/day for females of childbearing age
These are derived from biokinetic modeling: the IRL is the daily dietary intake estimated to raise blood lead level by 1 µg/dL, which is the threshold at which neurodevelopmental effects become measurable.
California Proposition 65 MADL
California's Maximum Allowable Dose Level (MADL) for lead is 0.5 µg/day — substantially stricter than FDA IRLs. The MADL is the threshold at which the California Office of Environmental Health Hazard Assessment estimates "no significant risk of reproductive toxicity even with lifetime exposure." It drives the Prop 65 warning labels you see on a lot of consumer products.
It's not a federal safety standard — it's California's framing — but it's a useful reference point because it's intentionally conservative.
The "5 PPB" framing
You'll see 5 PPB cited as a "safe threshold" for lead in baby food, particularly in the Lead Safe Mama / Tamara Rubin coverage. This is an ultra-precautionary advocacy number, not a legally binding standard, and it isn't tied to any specific dose-response calculation.
Why this matters: concentration (PPB) and dose (µg) are different things. If a baby food has 4 PPB lead in a 250 g serving, the actual lead intake from that serving is 1 µg — well below the FDA IRL. If a different product has 4 PPB in a 1000 g serving, the dose is 4 µg — closer to the IRL. The same PPB number can mean very different exposures depending on serving size. PPB without serving size is not a safety number; it's a marketing number.
The deprecated WHO PTWI
WHO's Provisional Tolerable Weekly Intake (PTWI) for lead was 25 µg/kg of body weight per week — about 250 µg/week for a 10 kg child. In 2010 the WHO withdrew the PTWI entirely, concluding that no level of lead exposure could be identified as having no associated effect.
That's not the same as saying any exposure is dangerous. It's saying: at every dose where they could measure, there was some effect, however small. The withdrawal was an honesty move, recognizing cumulative toxicity. It doesn't mean modern dietary exposure (well below the historical PTWI) is suddenly unsafe.
How to think about your own exposure
The math is simple:
Daily lead dose (µg) = lead concentration (PPB) × serving size (kg) × servings per day
Compare your estimated dose to the FDA IRL (2.2 µg/day children, 7.7 µg/day reproductive-age women). If you're well below it, you're in the range that current science considers acceptable risk. If you're regularly hitting or exceeding it from a single food source, that source warrants attention.
Don't lose sleep so someone else can get blog views.
Key facts
- FDA IRL (children): 2.2 µg/day
- FDA IRL (women of childbearing age): 7.7 µg/day
- California Prop 65 MADL: 0.5 µg/day
- "Lead Safe Mama" 5 PPB: advocacy framing, not a dose number
- WHO PTWI: withdrawn 2010
- Dose math: PPB × serving size × servings/day = µg/day
FAQ
What is the FDA IRL for lead?
2.2 µg/day for children, 7.7 µg/day for reproductive-age women.
What is the Prop 65 MADL?
0.5 µg/day — daily exposure with no significant reproductive toxicity risk over a lifetime.
What does "5 PPB" mean for baby food?
It's an ultra-precautionary advocacy benchmark. PPB without serving size is not a dose. Use the dose math.
Why was the WHO PTWI withdrawn?
WHO concluded no exposure level could be identified as having zero effect — methodological honesty about cumulative toxicity.
References
- U.S. FDA, "Interim Reference Levels (IRLs) for Lead in Food"
- California OEHHA, Proposition 65 Maximum Allowable Dose Levels for lead
- WHO/JECFA, withdrawal of PTWI for lead, 2010